The invention relates to a friction wheel drive associated with a unit belt drive of an internal combustion engine for a separate secondary unit, wherein a friction wheel cooperating frictionally in the wrap-around portion of a drive wheel of the internal combustion engine or other unit is in frictional connection with a drive wheel of the friction wheel drive of the secondary unit, wherein furthermore the friction wheel is taken out of engagement with the aforesaid friction partner in case of need by means of a control system.
A system of this kind has been proposed in a general configuration in Patent Application P 102 36 746, not disclosed earlier, without giving a concrete construction of the control system for the needed adjustment of the friction wheel relative to the drive wheel or to the belt.
It is the purpose of the invention to show a management, simple and reliable in operation, for a controlled friction wheel between an engagement active for the secondary unit and a disengaged position.
This purpose is accomplished in accordance with one aspect of the present invention in that the friction wheel is disposed in variable positions in a guiding device arranged on the machine side adjacent to the drive wheel or driven wheel relative to the drive gear or to the belt exterior in its particular circumferential contact area by means of the control device in order to turn the auxiliary unit on and off.
With the invention, a simple and reliably working management is achieved for a friction wheel arranged especially on the belt side of the friction wheel transmission that is associated with the secondary unit.
In a first embodiment of the invention, a simple and stable management system is achieved by the fact that it comprises guide plates disposed on both sides of the friction wheel at the same fixed distance apart, with equidistant, arcuate slots in which the friction wheel is disposed for displacement by means of the control system being guided in sliding movement by axial projections.
In order to avoid out-of-round running of the driving or driven wheel including the outer side of the belt, due to machine dynamics, on the one hand, and on the other hand to prevent increased wear, it is proposed in a further embodiment of the invention that the guiding system be spring mounted on the machine side. This can be accomplished, for example, by means of a silent block-like or rubber-and-metal arrangement which also serve to compensate inaccuracies.
A further proposal describes the settings of the friction wheel that are possible for a variable driving of the secondary unit, the control system comprising a servo motor arranged on the machine side for acting on a bell crank which is in communication with the friction wheel through a coupling rod serving to turn the secondary unit on and off and accordingly under tension or pressure. With this embodiment the control system can be advantageously adapted according to the space conditions at the combustion engine.
In order to damp shocks delivered to the coupling rod in some cases by the friction wheel, provision is made according to the invention for the coupling rod to be formed from two sections telescoping together, which thrust against one another with spring action when the secondary unit is turned on.
In another embodiment of the invention, the guiding system is a guiding link including the friction wheel in equidistant arrangement, which is equipped with bearings with rubber elastic cushioning. It can be in communication with a control system configured as previously described.
The invention finds use preferentially in a secondary unit serving as a coolant pump for an internal combustion engine whose drive wheel is controlled by the friction wheel through the Motronic map-controlled servo motor governed by parameters of the internal combustion engine. The servo motor can, in a known manner, operate hydraulically, pneumatically, electrically or magnetically.
The variable drive of the coolant pumps can be controlled in the scope of the invention, for example, also by only a single parameter. Preferably the temperature of the coolant of the internal combustion engine serves for this purpose.